As a prophylaxis or treatment method of thrombosis by dissolving the fibrin clot of arteriovenous thrombosis, a method of administering plasmin, a method of administering a plasminogen activator, a method of releasing a plasminogen activator by the administration of a medicament, a method of restraining a palsmin inhibitor, and the like, have been proposed and variously investigated but since these methods each of has some difficulties, only Urokinase is on the market as a fibrinolytic agent.
However, Urokinase has problems that the medicament cannot be orally administered, the medicament must be administered at a very high unit dosage, which results in increasing the cost of the medicament, and hence the development of compounds other than Urokinase, which can be orally administered and can be administered at a low cost, has been desired.
Hitherto, low molecular fibrinolytic agents which can be orally administered have been investigated but such fibrinolytic agents have not yet been practically used.
Recently, as one of the compounds possessing a fibrinolytic action, acylpeptides shown by the following general formulae (A) and (B) were proposed (European Patent Publication (Unexamined) Nos. 54,435 and 85,255); ##STR2##
However, for the clinical use as a fibrinolytic agent, the foregoing compounds are still insufficient in fibrinolytic activity. Almost all the foregoing known compounds show a low solubility in water, which makes it difficult to attain the sufficient pharamcological activity of these compounds and to form the preparations of these compounds.